Bone conduction telephone receiver



Patented June 1, 1954 UNITED STATES PATENT OFFICE 2,680,157 BONE CONDUCTION TELEPHONE RECEIVER Joachim Wolff, London,

Fortiphone pany of Great Britain Application July 3, 1950, Serial No. 171,921

Claims priority, application Great Britain July 25,

Claims.

This invention relates to bone telephone receivers that is to say to telephone screws. All these and other proposals which have been made present more or less serious practical defects. The known arrangements depending upon une pitch screws present the defect that since necessarily the threaded holes in which the L-shaped pole pieces are deformed present the disadvantage that there is only one position of adjustment in England, assignor to Limited, London, England, a cominvention adjustment of the gap of a bone conduction telephone receiver is effected through the medium of one or more resilient deformable members each or" which bears upon the flexible support for the armature and each of which is subjected to adjustable deformation by an adjustment member.

The adjustment members screws.

In the preferred embodiments the adjustment members act through resilient strip deformable According to this pole-piece-armature are preferably ber will produce a considerably smaller adjustment movement of the flexible support for the armature. Acordingly ne adjustment is rendered much easier. Locking means may be used can be locked, after adjustment, by means of lacquer or by locking grub screws or lock nuts.

Since the resilient deformable members partake to some extent of the nature of auxiliary diaphragms in contact with the main exible support for the armature (which may be regarded as the main diaphragm) they aiTect the frequency response of the receiver. This is, from the manufacturing and design point of View, an advantage and by suitably selecting the dimensions and materials of those members the frequency response of a receiver may be made to follow closely a desirable frequency characteristie. Itis, therefore, possible to produce a range of receivers of the same general design but with diierent frequency response characteristics to meet the requirements of dierent users.

By employing a plurality of symmetrically disposed strip resilient deformable members equally spaced round a flexible support for the armature-e. g. three at -it is possible to ensure exact parallelism between armature and pole piece across the gap.

The invention is illustrated in the accompanying drawings. Figures l to Il show one embodiment and Figure 5 shows a modification. In the drawings Figure l is an elevation partly in sec- Figure 2 is a plan with one arm of the three-armed flexible support for the armature broken away to show one of the resilientI deformable members underneath, Figure 3 is a plan o1" the ring magnet, and Figure 4 is a plan of the back plate and coil assembly of one embodiment while Figure 5 is an elevation partly in section, of a modification.

Referring to the drawings these show a bone conduction telephone receiver unit comprising three main sub-assemblies namely a baci; plate core and coil assembly A, a ring magnet B, and a front plate, armature and adjustment assembly C.

The sub-assembly A comprises a ferro-magnet back plate Al with an upstanding central pole piece A2 on which is a coil A3 and which has a ring of six holes of which three alternate holes A4 are large and the other three [it small. The two additional small holes A@ pass the leads to the coil A3.

The ring-magnet sub-assembly consists of -one part, namely the ring magnet B itself, which 'is formed with a ring of six haii-holes El inline with the holes Afl and A5 when the sub-assemblies are put together.

The sub-assembly C, with which this invention is concerned consists of a top plate Ci on which is carried, by means of screws C2 screwing thereon, a flexible support or diaphragm member for the armature. rfhis support is in the form ol a three armed spider' C3 the cuter ends of the arms of which are drilled to pass the shanks of the screws C2. Each screw C2 passes iirst through a hole in the appropriate spider arm, then through a spacing collar Cil, then through a hole in the end of a deformable adjustment member C5. The centre of the spider has a central hole and the armature structure, which is not shown in detail since it forms per se no part of this invention is carried from the centre of the spider by means 01"' its two parts Ct, C'i which screw together to clamp the centre of the spider between them. Deformable adjustment strips which are of springy, deformable metal, lie

underneath the arcuate outer parts of the spider arms and each has an upturneol end C8 which bears against the underside of the appropriate arcuate outer part about half way between its anchoring screw C2 and the radial part of the arm. Adjustment screws C9 screw into tapped holes in the top plate Cl and each, when screwed up, presses up from underneath against the appropriate adjustment strip C5 about a third of the way along from its anchored end.

The three sub-assemblies are put together in line as shown in Figure l with the magnet B between the sub-assemblies A and C. The large holes All are big enough to pass the heads of the adjustment screws C9 which lie in said holes and are accessible for adjustment. The small holes A5 which are countersunk on the under side pass the shanks of screws Ci@ which screw into tapped holes in the top plate Cl and hold the sub-assemblies together with the lower face of the armature spaced by a small (adjustable) air gap from the top face of the central pole piece A2 and the top face of the top plate Ci which is coplanar with the said pole piece face.

As will be apparent, with this arrangement adjustment of the screws C9 varies the pressure with which the ends of the adjustment members C5 bear against the spider arms and therefore varies the armature-pole piece gap. Further, since the members C5 are resiliently deformable they bend under the pressure of the screws C9 so that a relatively large longitudinal movement of one o these screws produces a considerably smaller movement of the spider arm affected. Accordingly close adjustment is facilitated and the hereinbefcre described defects of known able strip member intermediate arrangements are avoided or greatly reduced. rIhe screws CQ may be locked by painting them with lacquer or any other convenient locking means may be used if required. As will be obvious to those skilled in the art other means known per se may be used instead of the illustrated screws CS for adjusting the member C55 e. g. adjustment wedges, rollers, cams or bars.

A telephone unit as above described and illustrated is mounted in a suitable casing (not shown) -for example of the material known under the registered trade mark of Bal elitesuch mounting being most conveniently tted by drilling and tapping the centre of the upper or clamping part of the armature structure, and employing a bolt which passes through the centre of the back of the casing into this drilled and tapped hole and therefore holds the armature firmly up against the inside of the back of the casing. This holding bolt is thus the sole support for the telephone proper. In use pressure sound waves are transmitted to the back of the casing and then through the casing to the front thereof, which is made of suitable hollow shape as known per se to t comfortably and efciently against the sound receiving bone of the wearer.

In the modication shown in Figure 5 each of the deformable strip shaped adjustment members C5 of Figure 1 is replaced by a coiled spring C55 which may be helical or, as shown spirohelical. rIhe compression of this spring is adjusted by an adjustment screw C59 and the upper end of the spring i. e. the end remote from the screw C59 has inserted therein the stern part oi a taper headed member C58 which performs a function similar to that of the parts C8 of Figure l and bears against the underside of the appropriate arm of the spider C3, where, if desired, a small dimple may be formed to receive the point of the head of the member C58. It is thought that the remainder of Figure 5 will be self-evident from the description already given of Figure 1, like parts in both figures carrying the same references.

I claim:

l.. In a bone conduction telephone receiver unit having an armature supported adjacent a magnetic pole piece by iiexible support means providing an air gap between said armature and said pole piece, adjustment means for adjusting said air gap said adjustment means comprising a resilient deformable member engaging said ilexible support means and constituted by an anchored strip and means engaging said deformthe anchorage of said strip member and where said strip member engages the flexible support means, adjustably to deform the same.

2. A unit as claimed in claim l wherein said flexible support means is a iiexible spider having arms one of which is engaged by the resilient deformable member.

3. A unit as claimed in claim l wherein said flexible support means is a iiexible spider having arms each having a radial portion extending into an arcuate portion anchored at the far end and one of which is engaged by the resilient deformable member between the ends of said arcuate portion.

ll. In a bone conduction telephone receiver unit having an armature supported adjacent a magnetic pole piece by flexible support means providing an air gap between said armature and said pole piece, adjustment means for adjusting said air gap, said adjustment means comprising a resilient deformable member engaging said ilexible support means and means engaging said deformable member adjustably to deform the same, said Iiexible support means being a flexible spider having a plurality of arms and said resilient deformable member being a strip anchored at one end and having its other end upturned to engage an arm of said spider.

5. In a bone conduction telephone receiver unit having an armature supported adjacent a magnetic pole piece by flexible support means providing an air gap between said armature and said pole piece, adjustment means for adjusting said air gap said adjustment means comprising a resilient deformable member engaging said flexible support means and constituted by an anchored strip and a screw engaging said deformable strip member intermediate the anchorage of said strip member and Where said strip member engages the ilexible support means, adjustably to deform the same.

References Cited in the le of this patent UNITED STATES PATENTS Number Re. 21,030 990,275 1,356,156 1,404,817 1,939,922 m 2,000,165 2,062,37 2 2,264,684 2,410,805 2,459,325 15 2,463,785 2,500,541

N nmber Name Date Greibach Mar. 14, 1939 Koltonski Apr. 25, 1911 Kurman Oct. 19, 1920 Werber Jan. 31, 1922 Rockwell Dec. 19, 1933 Erickson May 7, 1935 Nicholides Dec. 1, 1936 Weidenman, Sr. Dec. 2, 1941 Black, Jr Nov. 12, 1946 Knowles Jan. 18, 1949 Lybarger Mar. 8, 1949 Greibach Mar. 14, 1950 FOREIGN PATENTS Country Date Great Britain Aug. 17, 1933 

